Papers by Keyword: Energy Release Rate

Abstract: The process of crack propagation from the initial pore in the microstructures of WC-Co alloys with different volume fraction of the cobalt phase was studied by simulation of the stressed state by the finite element method. A calculation of the energy release rate during the propagation of crack through sections which consist of the carbide grains and the cobalt phase was made. It is shown that the strain energy release rate increases with crack propagation in WC grains and decreases with crack propagation in the intermediate layers of cobalt. The maximum stresses required for the destruction of the cobalt layer determine the strength of the entire microstructure. The strength of the alloy increases when decreasing pore diameter and increasing the cobalt phase fraction.

Abstract: Fiber/matrix debonding in transverse tensile loading of a unidirectional composite is analyzed calculating energy release rate (ERR) for interface crack propagation. Non-uniform fiber distribution (local hexagonal fiber clustering) is assumed in the model. The matrix region containing the central fiber with the debond and the 6 surrounding fibers is embedded in a large block of homogenized composite which has the same fiber content as the region analyzed explicitly. Some of the fibers surrounding the central fiber may also have a debond. The effect of the local clustering and of the presence of other debonds on magnification of the ERR is analyzed.

Abstract: The performance of bearing has great influence on mechanical components and fatigue is one of the most important failure modes. However, the occurrence of crack is inevitable in the process of manufacture and usage. Research on characteristics of crack propagation is an important supplement and development to the traditional fatigue analysis method and test. The FE model of a bearing inner ring with a semielliptical crack is established in ABAQUS to carry out further analysis of crack propagation. The crack propagation characteristics with different initial crack size are analyzed and the energy changing law during crack propagation has been investigated under cyclic loading though FE calculation. The results provide valuable guidance for further study on fatigue crack propagation of bearings.

Abstract: The delamination growth may occur in delaminated piezoelectric shell subjected to external load and it will further cause structural failure. Based on the variational principle of moving boundary and considering the contact effect between delamination regions, in this paper, the nonlinear governing equations for the delaminated piezoelectric shell under electro-thermo-mechanical loadings are derived, and the corresponding boundary and matching conditions are given. At the same time, according to the Griffith criterion, the formulas of energy release rate along the delamination front are obtained and the delamination growth is studied. In the numerical calculation, the energy release rate and delamination growth of axisymmetrical piezoelectric cylindrical shell are analyzed, and the effects of voltage, temperature and humidity, mechanical load, delamination length and depth on delamination growth are discussed.

Abstract: The different influencing regular of fly-ash fractiontype of fibre (steel fibre and polypropylene fibre) and fibre fraction on the mechanical property and fracture behavior of Reactive Powder Concrete (PRC) are studied. Fracture mechanical properties of RPC is researched in double-K fracture model and fracture energy release rate G . Test results show that the crack propagation of RPC with steel fibers is limited. Its fracture toughness and pre-critical crack length is largely enhanced. Double-K fracture model and fracture energy release rate G are consistent with describing the fracture behavior of RPC.

Abstract: Arbitrary, non-planar progressive fracture analysis is of critical importance to the integrity of structures. While significant progress has been made in the last 25 years, there are still technical issues regarding computational expense, robustness, and accuracy. Based upon the recent significant enhancements available through the use of multicomplex finite element methods, a new high-order progressive strain energy based progressive crack growth algorithm is proposed.

Abstract: The present study evaluates stress fields, the stress intensity factor and energy release rates at the time of the cracking in a composite material. Our problems are formulated using two materials having different parameters such as the shearing modulus and the Poissons ratio. After having determined the displacement and stress fields, one homogenized the latter in order to allow comparing the results with those of other researchers. During the propagation of the main crack, the surrounding dislocation induces two effects: amplification effect which increases the stress at the main crack-tip and a shielding effect which reduces the propagation of the main crack. Finally, Energy Release Rates (ERR) associated to the different transformation inside the damage zone is evaluated on the basis of the superposition of all energies: the energy due to the main crack, the energy due to the existing dislocation and the energy due to the interaction.

Abstract: Critical strain energy release rate in CFRP composites characterizes the delamination resistance. More study is still needed to measure the critical strain energy release rate in sliding shear mode (G_IIC) considering various factors that influence its measurement. This study evaluates one of the influencing factors, the starter defect. Two types of on thin, unidirectional CFRP composites with one having thin film insert as starter defect and another one with pre-crack under Mode II loading were prepared and tested in three point bending end notch flexure (3ENF) test. It was found that the (G_IIC) of the former was more than twice higher than that of the latter, supposedly due to the presence of resin rich region in the former.

Abstract: A laminated beam containing an initial delamination subjected to thermal gradient is analyzed on the basis of classical beam theory. The axial forces are induced in the parts of the constituent beams above and below the delamination. For the case where crack faces are open, a nonlinear equation for determining the in-plane forces is derived by modeling the delaminated part as two lapped beams hinged at both ends, and by imposing the compatibility condition of the deformations of the two beams. Numerical solutions are obtained for some model beams. It is shown that the relative displacement at the center of the delamination increases gradually with the increase very rapidly, i.e., local delamination buckling occurs. Energy release rate is small for temperature gradient below the critical value, but it takes a large value when the temperature gradient is increased beyond the critical value.

Abstract: The Failure of the Interface between Fiber and Matrix under Transverse Loading is the Key Factor Controlling the Failure Process in Composite Materials. the Debonding Process of a Fiber within a Unidirectional Composite is Studied by Finite Element Analyses Using a Representative Volume Element. the Energy Release Rate is Calculated for Different Fiber Volume Fractions. Two Load Cases are Taken into Account, Pure Transverse Tension and Shear Loading.